In a combustion chamber of a diesel engine as well as aftertreatment components, malfunctions of the air inlet valve, exhaust valve, and/or injector may lead to knock, misfiring, and out-of-phase combustion. To detect these malfunctions, an engine control module (ECM) usually relies on in-cylinder pressure measurements at particular crank angles. For example, pressure measurements may be obtained by a quartz pressure sensor installed in the combustion chamber or aftertreatment components. However, the measured pressure data are reliable only after averaging tens of engine cycles, and thus, result in significant delays in engine and/or aftertreatment component fault detection. The delay prevents the ECM from promptly adjusting control parameters to avoid catastrophic events of engine operation. Therefore, it is desirable that the sensor provides timely feedback to the ECM as early as the first engine cycle.
Furthermore, a chemical reaction status in the combustion chamber or an aftertreatment component may be indicated by multiple characteristic parameters, such as pressure, temperature, and ion current intensity. Therefore, it may be helpful that a sensor can measure these characteristic parameters at the same location and combine them to determine the unique chemical reaction condition. In addition, it may also be beneficial if the sensor has a self-validation function to monitor and detect sensor faults using its own measurements.
An apparatus for detecting knock in an internal combustion engine is described in U.S. Pat. No. 6,789,409 to Tanaya et al. (“the '409 patent”). The '409 patent describes an apparatus for accurately distinguishing knock from normal noise in the internal combustion engine. The apparatus includes an ion-current detection device for detecting an ion current flowing between the electrodes following combustion in the combustion chamber, a knock detection device for detecting knock occurring following an abnormal rise in either pressure or temperature in the combustion chamber, a center-of-gravity calculation device for calculating a gravity position of an ion current waveform, and a knock determination device for determining knock or noise based on outputs of the knock detection device and the center-of-gravity calculation device.
Although the knock detection apparatus described in the '409 patent may be effective for detecting knock in the internal combustion engine, it may be problematic. For example, the knock detection apparatus described in the '409 patent relies on an abnormal rise in either the steady-state pressure or the steady-state temperature to detect the knock, and thus may not be capable of providing timely and accurate feedback to the ECM shortly after startup, as the machine has not been operated long enough for the temperature or pressure sensor to reach steady-state operation. Furthermore, although the apparatus described in the '409 patent measures multiple characteristic parameters (e.g., ion current, pressure/temperature, etc.), these measurements are obtained from sensors that are located in different parts of the engine. As a result, the apparatus described in the '409 patent may not be able to determine a chemical reaction status corresponding to a single location, as the pressure measurement data may have been gathered from a different part of the engine than the ion current data. In addition, the apparatus described in the '409 patent may lack self-validation functions.
The disclosed ion-based triple sensor is directed towards overcoming one or more of the shortcomings set forth above.